Pipe conveyors

ABSTRACT

A conveyor system may include a pipe conveyor with a head end, a tail end, and an inclined section. The conveyor system may also include a conveyor belt including a first portion and a second portion. The conveyor belt may form a pipe shape when the first and second portions of the conveyor belt are overlapped. The pipe shape may extend from a pipe closing point to a pipe opening point and may enclose two or more longitudinally spaced-apart centering structures. The centering structures may allow for self-bridging of a bulk material carried in a pipe volume above each centering structure. Means of implementing this material-transport principle within a pipe conveyor system are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of InternationalApplication No. PCT/US2014/029039, filed Mar. 14, 2014, and entitled“PIPE CONVEYORS”, which claims priority to U.S. Application No.61/798,247, filed Mar. 15, 2013, and entitled “PIPE CONVEYORS”, both ofwhich are hereby incorporated by reference herein in their entiretiesfor all purposes.

TECHNOLOGICAL FIELD

The technological field generally relates to pipe conveyors, and moreparticularly to steep angle pipe conveyor systems and vertical pipeconveyor systems.

BACKGROUND

One type of conveyor for transporting material is a pipe conveyor, whichcan be used to protect the material being transported by enclosing it.As such, pipe conveyors are often used in situations where spillage ordust may be an issue or where use of conventional conveyor systems maybe too costly or hazardous due to environmental or population concerns.Pipe conveyers may be useful, for example, to convey bulk materialbetween the phases of mining, processing, and storage.

Some pipe conveyors transport material in a circular cross-sectionformed by overlapping belt edges and using idlers arranged in ahexagonal pattern to form the tubular pipe-like shape. At the loadingpoint, these systems provide a trough or flat conveyor for loading ofthe material. After loading the material, the belt is formed into a pipeshape for the transport length of the system and re-opened at thedestination for the unloading of the material in the standard manner ofa troughed or flat conveyor. Because the material is enclosed by thebelt during transport, spillage, scattering, pollution, and flying dustmay be reduced. These systems also may allow the pipe conveyor tomaneuver both vertical and horizontal curves that may be difficult forconventional conveyors to pass through. Also, because pipe conveyors canload and discharge the bulk material in the conventional manner,standard equipment may be used at the head and tail ends.

Pipe conveyors are also useful in situations in which the conveyorlayout requires horizontal and/or vertical curves, especially, when theconveyor layout includes a vertical rise or fall. Conventional pipeconveyors, however, are generally limited to being used in conveyorsystems with vertical angles of less than 30 degrees as measured from ahorizontal axis. While some pipe conveyor designs that allow for pipeconveyors to rise at vertical angles greater than 30 degrees, suchsystems were proposed more than a quarter of a century ago but haveapparently not found successful commercial implementation.

In such conventional systems, the pipe forms a continuous tube. Liftingof the carried material appears to rely on a continuous carry/fallsequence that transports slugs of material for some distance up the tubeby means of friction with the pipe walls until the slug collapses andthe material falls back down the pipe to a higher level than where itbegan the previous carry/fall cycle. While prominent pipe conveyorvendors and materials-handling universities have demonstrated inexperiments that such a transport mechanism can occur, it appears thatdifficulties with this approach have, at least to date, prevented suchpipe conveyors from being offered for sale.

There are a number of significant difficulties or disadvantages inherentto such systems, which would be manifested if pipe conveyors operatingon the continuous-tube principle could be commercialized. One weaknessis that the efficiency of transport is likely to be highly dependent onthe bulk flow properties of the carried load, which may varycontinuously with some partially-processed materials. Another isthat—under certain feed conditions—a long void could form below a filledlength of pipe, where the filled length is temporarily supported bynatural arching or bridging. Such a column of material—having beenlifted to a significant height—could then break free, resulting in asudden collapse of the material in the column, and causing the kind ofcatastrophic air-blast sometimes associated with hung-up ore passes inunderground mines. Yet other limitations of such designs are thatspecial procedures using loose flexible plugs are required to empty theconveyor, and that these designs have only been proposed for conveyingin the upwards direction.

Another significant limitation of steep or vertical pipe conveyorsystems is that the tensile capacity of the pipe belt increases only indirect proportion to the width of the belt. However, the weight of thematerial enclosed within the tube and supported by the tensile capacityof the pipe belt increases roughly in proportion to the square of thewidth of the belt. Therefore, as a designer of a steep or vertical pipeconveyor attempts to increase tonnage by increasing the effectivediameter of the carrying tube, it may be found that the tensile capacityof the pipe belt quickly becomes the limiting constraint. Even whenintermediate traction drives are provided, this adverse relationship mayresult in the intermediate drives having to be spaced much more closelythan would otherwise have been necessary.

Another possible disadvantage of such steep or vertical pipe conveyorsystems is that they may be prone to an unacceptable amount of leakageof carried material fines between the overlapping flaps of the pipebelt. Since the material in the tube is continuously displaced by thecarry/fall transport mechanism, there is less opportunity for materialto cake at and seal the junction between the overlapping pipe beltflaps.

In another type of steep or vertical pipe conveyor system, a tensionelement separate from the pipe belt, such as a chain or cable, carries aseries of stiff diaphragms within the tube formed by the pipe belt. Thediaphragms are configured to stand in planes perpendicular to the mainaxis of the tube, and to carry most of the weight of the material insteep sections of the pipe conveyor, and transfer the weight of thatmaterial to the tension element. The tension element in turn issupported by a drive means at a location beyond the conveyor dischargepoint. The purposes of such a configuration are apparently to liftdiscrete volumes of material carried by the discs, and to relieve thepipe belt of the tension-carrying role, so that the belt's primary rolebecomes that of enclosing the material. A major limitation of such adesign is that, for dense materials or high lifts, the tension accruedby the tension element quickly rises to exceed its tensile capacity.Therefore the approach becomes impractical for the high liftsencountered in some applications such as mining. Another significantdisadvantage of such systems is that the tension element is in directcontact with the load so that if the load is an abrasive and somewhatsticky material, such as a moist ore, a high rate of wear would occur onthe tension element and on the means used to drive it, such as asprocket in the case where the tension element is a chain. Yet anotherdisadvantage of such an approach is that the rigid discs described aresusceptible to damage by larger lumps of ore, as is the tension chain.

SUMMARY

One embodiment of a conveyor system may include a pipe conveyor with ahead end, a tail end positioned at an elevation different than that ofthe head end, and an inclined or vertical section between the head endand the tail end. The conveyor system may also include a conveyor beltwith a first portion and a second portion, the conveyor belt configuredto form a pipe shape when the first and second portions of the conveyorbelt are overlapped. The conveyor system may also include an auxiliarybelt, referred to herein as a bridging belt, carried internal to thetube formed by the conveyor belt, and carrying throughout its endlesslength a series of flexible structures intruding across the section ofthe internal space formed by the conveyor belt. These flexiblestructures may be primarily configured to perform a centering functionthat promotes the bridging or self-arching behavior of a volume ofmaterial carried within the tube, thereby causing tangential frictionalforces at the walls of the tube to be the primary means of support forthe weight of the volume of material. The bridging belt may further beconfigured to carry the flexible structures only on an upper side of thebridging belt, and also to lie at the bottom of the troughed conveyorbelt as the two belts progress towards a material-loading zone of theconveyor system. The conveyor system may further be configured tobriefly route the bridging belt on a path displaced away from theconveyor belt beyond the discharge pulley of the conveyor belt, so as toallow for belt-cleaning of the conveyor belt.

Another embodiment of a conveyor system may include a pipe conveyor witha head end, a tail end positioned at an elevation different than that ofthe head end, and an inclined or vertical section between the head endand the tail end. The conveyor system may also include a conveyor beltwith a first portion and a second portion. The conveyor belt may form apipe shape when the first and second portions of the conveyor belt areoverlapped. The conveyor system may also include a series of flexiblestructures attached to the inner wall of the conveyor belt and intrudingacross the section of the internal space formed by the conveyor belt.These flexible structures may be primarily configured to perform acentering function that promotes the bridging or self-arching behaviorof a volume of material carried within the tube, thereby causingtangential frictional forces at the walls of the tube to be the primarymeans of support for the weight of the volume of material.

Another embodiment of a conveyor system may include a pipe conveyor witha head end, a tail end positioned at an elevation different than that ofthe head end, and an inclined or vertical section between the head endand the tail end. The conveyor system may also include a conveyor beltwith a first portion and a second portion. The conveyor belt configuredmay form a pipe shape when the first and second portions of the conveyorbelt are overlapped. The conveyor system may also include one or morenarrow elongate longitudinal connectors (such as a rope, wire rope,chain, or conveyor belt) carried internal to the tube formed by theconveyor belt. These elongate connectors may support throughout theendless length of the elongate connector a series of flexible centeringstructures intruding across the section of the internal space formed bythe conveyor belt. These flexible centering structures may be primarilyconfigured to perform a centering function that promotes the bridging orself-arching behavior of a volume of material carried within the tube,thereby causing tangential frictional forces at the walls of the tube tobe the primary means of support for the weight of the volume ofmaterial. The elongate connectors may further be configured to carry thecentering structures centered about the long axes of the elongateconnectors. The conveyor system may further be configured to brieflyroute the elongate connectors on a path displaced away from the conveyorbelt beyond the discharge pulley of the conveyor belt, so as to allowfor belt-cleaning of the conveyor belt.

Another embodiment of a conveyor system may include any of the conveyorsystems described above, but further including a number of intermediatefriction drives installed along the course of the inclined portion ofthe conveyor. The intermediate friction drives may engage externalsurfaces of the pipe conveyor belt. In such embodiments, thestably-resting material contained within the discrete cells formed bythe flexible centering structures may provide more resistance to lateralcompression of the conveyor pipe than is available in the case ofcontinuous-tube pipe conveyors where the carried material iscontinuously falling back to some degree. Therefore the intermediatefriction drives may be take advantage of this increased resistance tolateral compression of the pipe walls by allowing an increased biasingforce and power input from the intermediate friction drives.

Another embodiment of a conveyor system may include any of the conveyorsystems described above, where the material to be transported is of asufficiently fine granular size distribution as to eliminate any concernof large lumps of material being trapped between the centeringstructures and a closing pipe belt, so that the centering structures maybe of a relatively rigid construction when compared to the stiffness ofthe pipe conveyor belt.

Another embodiment of a conveyor system may include any of the conveyorsystems described above, where a feeding device at the loading zone isconfigured to feed the material to be transported at a rate that onlyfractionally fills the carrying segments defined by the centeringstructures, providing for a lower transported weight per unit lift ofpipe belt, and therefore allowing for greater lift heights between pipebelt drives.

Another embodiment of a conveyor system may include a pipe conveyor. Thepipe conveyor may include a head end, a tail end positioned at anelevation different from the head end, an inclined section between thehead end and the tail end, and a conveyor belt. The conveyor belt mayinclude a first portion and a second portion. The conveyor belt may forma pipe shape when the first and second portions of the conveyor belt areoverlapped. The pipe shape may extend from a pipe closing point to apipe opening point and may enclose two or more longitudinallyspaced-apart centering structures. At least one of the two or morelongitudinally spaced-apart centering structures may enableself-bridging of a bulk material carried in a pipe volume above the atleast one of the two or more longitudinally spaced-apart centeringstructures. The self-bridging of said bulk material causes a weight ofsaid bulk material to be primarily supported by interaction of said bulkmaterial with walls of the pipe shape.

In some implementations, the at least one of the at least one of the twoor more longitudinally spaced-apart centering structures is sufficientlyflexible to conform to the pipe shape when a lump of bulk material ispinched between the at least one of the two or more longitudinallyspaced-apart centering structures and the conveyor belt.

In some embodiments, the two or more longitudinally spaced-apartcentering structures are carried on at least one endless elongateconnector (such as a rope, wire rope, chain, or conveyor belt) notjoined to the conveyor belt. The at least one endless elongate connectormay include at least one bridging belt that carries the two or morelongitudinally spaced-apart centering structures on one face of the atleast one bridging belt. An opposing face of the at least one bridgingbelts may rest against a carry-side medial surface of the conveyor belt.

In some implementations, the at least one of the two or morelongitudinally spaced-apart centering structures may include mountingflanges. In such implementations, the mounting flanges and the at leastone bridging belt may be narrow relative to a circumference of the pipeshape. Further, the at least one of the two or more longitudinallyspaced-apart centering structures may include first and secondsubstantially circular portions joined at a common apex by a narrowconnecting portion.

In some embodiments, the at least one endless elongate connector mayinclude a wire rope. In such embodiments, the two or more longitudinallyspaced-apart centering structures may include two or more sphericalcentering structures in which the wire rope passes through diametricalaxes of the two or more spherical centering structures. The conveyorsystem may further include at least one guide wheel having peripheralrecesses that are sized to accept at least one of the two or morespherical centering structures as the at least one of the two or morespherical centering structures passes the at least one guide wheel.

In some embodiments, at least one bend pulley situated beyond adischarge pulley of the conveyor system may guide the at least oneendless elongate connector on a path displaced away from a path of theconveyor belt.

In some implementations, the at least one of the two or morelongitudinally spaced-apart centering structures may attach to the atleast one endless elongate connector in such a way as to dispose the atleast one centering structure substantially symmetrically about the atleast one endless elongate connector.

In some embodiments, each of the two or more longitudinally spaced-apartcentering structures may be directly attached to a carry-side medialsurface of the conveyor belt. In some of these embodiments, at least oneof the two or more longitudinally spaced-apart centering structures maybe adhered to the carry-side medial surface of the conveyor belt.

In some embodiments, the conveyor system may include at least oneintermediate friction drive at an inclined portion of the pipe conveyor.The least one intermediate friction drive may engage external surfacesof the conveyor belt.

In some implementations, the two or more longitudinally spaced-apartcentering structures may be closely spaced and configured to stiffenopposing walls of the pipe belt against a biasing applied by tractioncomponents of the at least one intermediate friction drive.

In some embodiments, the two or more longitudinally spaced-apartcentering structures may include an arch shaped centering structure.

In some implementations, the at least one intermediate friction drivemay include a friction drive tire and/or the at least one intermediatefriction drive may include traction drives biased against opposingflattened walls of the conveyer belt with the two or more longitudinallyspaced-apart centering structures spanning between the flattened walls.

In some embodiments, at least one of the two or more longitudinallyspaced-apart centering structures may include one or more footingsintegrally molded with a cylinder.

In some embodiments, the conveyor system may include a feeding devicethat feeds the bulk material at a rate that only fractionally fills twoor more carrying segments defined by the two or more longitudinallyspaced-apart centering structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a vertical section of a vertical pipe conveyor loaded withbulk materials.

FIG. 2a shows a partial perspective view of an open trough of a pipeconveyor belt upstream of the material loading zone of a pipe conveyorsystem, with a bridging belt carrying centering arches and laid on thebottom of the pipe belt.

FIG. 2b shows a perspective view of a centering structure in the form offlexible arch carried on a bridging belt.

FIG. 2c shows a longitudinal section of a length of the pipe conveyorbelt, with flexible arches supporting the bulk material in a series ofdiscrete cells.

FIG. 2d shows in elevation a longitudinal section of a length of thepipe conveyor belt, with centering arches configured to allow higheramounts of traction to be applied via intermediate traction drives.

FIG. 3a shows a transverse section of a pipe conveyor belt in a materialloading zone, illustrating how an open arch provides a route for lumpymaterial to avoid being pinched by the enclosing walls of the pipe belt.

FIG. 3b shows a transverse section of pipe conveyor where the pipe beltforms a rounded rectangle about an enclosed centering structure.

FIG. 3c shows a perspective view of a pattern for flat material that isformed into a centering structure.

FIG. 4 shows a perspective view of a portion of a pipe conveyor beltwith centering structures attached directly to the medial portion of thepipe conveyor belt.

FIG. 5a shows another embodiment of a centering structure for a pipeconveyor of a rounded rectangular transverse section, where thecentering structure takes the form of a fully-closed domed cylinder.

FIG. 5b shows a lateral view of the centering structure illustrated inFIG. 5b .

FIG. 6a shows a transverse sectional view of a centering structurepositioned in a pipe conveyor which has a traditional circulartransverse section.

FIG. 6b shows a perspective view of the centering structure of FIG. 6a ,embodied in the form of flexible arch carried on a bridging belt that isnarrow relative to the circumference of the pipe tube.

FIG. 6c shows a lateral elevation of the centering structure of FIG. 6bmounted on the bridging belt.

FIG. 7 shows a lateral elevation of a centering structure configured forattachment by adhesion to the bridging belt.

FIG. 8 illustrates an embodiment where the centering structures arecentrally rather than laterally attached to the longitudinal connectors.

FIG. 9a illustrates implementation of the centering structure andbridging belt principle in a vertical pipe conveyor system.

FIG. 9b shows cross section of the pipe tube of FIG. 9a enclosing acentering structure and bridging belt.

FIG. 10 shows a schematic elevation view of a system for separating thepaths of the bridging belt and the pipe belt at the discharge pulley ofthe pipe conveyor system.

FIG. 11 shows a schematic perspective view of another arrangement forseparating the paths of the bridging belt and the pipe belt at thedischarge pulley of the pipe conveyor system.

FIG. 12 illustrates a schematic elevation view of the tail end of a pipeconveyor system upstream from the loading zone where a locally convexconveyor path aids in holding the bridging belt stably on the bottom ofthe pipe conveyor trough.

DETAILED DESCRIPTION

Described herein are vertical and steep angle pipe conveyor systems thatmay be used to transport materials from one location to anotherlocation. Pipe conveyor systems may be suited for use in, for example,mines that include steep or vertical angles that are greater than thesurcharge angle of the carried material. These pipe conveyors mayinclude a conveyor belt that is formed into a pipe-like shape to definea space that contains the material to be transported by the conveyor.These pipe conveyors may also include structures within the pipe-likeshape configured to enable bridging of the carried material and toprovide for dividing a continuous pipe space into a longitudinalsequence of substantially discrete cells.

Bridging properties of a bulk material are well known to designers ofbulk materials equipment, such as silos, hoppers, chutes, feedingdevices, and the like. However, whereas the bridging is usuallyperceived as a problem to be avoided in the design and operation of suchequipment, the property may be advantageously utilized to enable a newmode of material transportation in steep or vertical pipe conveyorsystems.

FIG. 1 is a schematic elevation view of a longitudinal section of a pipeconveyor where a conveyor belt 102 has been formed into a vertical tubeor other pipe shape 101 by overlapping a first portion 110 and a secondportion 112 of the conveyor belt 102. A volume of bulk material 103carried by the pipe conveyor system is contained within the verticaltube 101. The volume of bulk material may be situated above a partialvoid 105 and separated from the partial void by a centering structure104 that at least partially spans between the walls formed by theenclosing belt 102. The centering structure 104 may be highly flexible,having far less stiffness than is required to support the weight of theportion of bulk material 103 carried above the centering structure 104.However, it is a property of many bulk materials that they tend todisplay bridging behavior to at least some degree. The centeringstructure 104 serves to support an arch or bridge of material 106 thatspans between the walls of the tube. The arch of material 106 may carryload in the manner of conventional structural arches, transferring mostof the weight of the volume of bulk material 103 directly into the wallsof the tube. This material arching continues throughout the column ofmaterial so long as the height of the column is large relative to itsdiameter.

Even if the centering structure only partially or irregularly spansacross the diameter of the tube, it may still serve the function ofsubstantially supporting the bridging of the bulk material. This latteris true even if the centering structure is substantially distorted ordisplaced when the pipe belt is folded into a closed tube. In some ofthe embodiments that follow, the principle of the centering structure104 is embodied in centering structures of differing forms. It ispossible to utilize the principle described above in a very great rangeof shapes and configurations of centering structures adapted to thepurpose of promoting bridging within a steep or vertical pipe conveyortube.

The principle of the centering structure 104 may be usefully applied toconveyor pipes of round, oval, rounded rectangular and othercross-sectional forms. The segmentation of the load provided bycentering structures may be useful for pipe conveyors rising or fallingat angles greater than the surcharge angle of the bulk material. Thecentering structure principle may be embodied equally successfully inpipe conveyors that are raising material or lowering material.

FIG. 2a shows the open trough of a pipe conveyor belt 205 downstream ofthe material loading zone of a pipe conveyor system. An endless elongateconnector, such as a bridging belt 201, carrying centering arches 202 ispositioned on the bottom of the pipe belt trough. The pipe conveyor belt205 is ready to receive the bulk material loaded into the trough of thepipe conveyor belt 205 from above.

One function of the bridging belt 201 is to carry a continuous series ofcentering structures spaced from each other at a predetermined distanceon a circuit that may run mostly within the pipe conveyor belt. Anotherfunction of the bridging belt is to carry the series of centeringstructures into the loading zone within the trough of the pipe conveyorbelt and to stably position the series of centering arches prior tocoverage of the centering arches by loaded material.

The predetermined spacing between the centering structures may beselected to optimize the level of horizontal pressure developed at thebase of each segment or cell, and to limit the amount of slide-back asthe bulk material is drawn through the first vertical curve thatconnects the horizontal portion of the pipe conveyor to the steep orvertical portion. Another spacing consideration is to place thecentering structures sufficiently close together so that even if aparticular centering structure is torn off or does not produce thedesired bridging, the adjacent centering structure is close enough toallow it to function in the desired manner. In some embodiments, theseconsiderations may lead to a spacing of the centering structures that isperhaps two to ten times the largest diametral dimension of the pipebelt.

An advantage of using a narrow rubberized belt—such as is used inconveyor belting—to act as an elongate endless connector between thecentering structures is that the bridging belt 201 can be formulated toabsorb a good portion of the wear imparted by the material being loadedinto the trough of the pipe belt at the loading zone. Furthermore,because such a bridging belt can be of low strength and does not requirethe type of specialized transverse stiffness called for in a pipe belt,the bridging belt can be a low-cost belt.

FIG. 2b shows a centering structure 202 in the form of a flexible archcarried on the bridging belt 201. The centering structure 202 may beconfigured from a length of stiff yet flexible material, such asconveyor belting whose carcass is either fabric or steel cord. Thecentering structure may further be configured to have sufficientstiffness to roughly maintain its form when material of a predeterminedtypical density and size distribution is loaded from above the centeringstructure and into the trough of the pipe conveyor.

The centering structure 202 may be attached to the bridging belt 201 bymechanical fasteners 204 or by other suitable attachment means, such asvulcanization or adhesion. In this embodiment of the centering structure202, a space 206 defined between the centering structure and thebridging belt 201 may diminish the likelihood that a lump of loadedmaterial is pinched between the pipe conveyor belt and the centeringstructure 202 when the pipe conveyor belt is being formed from a troughinto a pipe.

The centering structure may further be configured with sufficientflexibility so that the centering structure deforms instead of anysignificant deformation being imposed on the wall of the pipe conveyorbelt if a lump of material becomes pinched between the pipe conveyorbelt and the centering structure when the pipe conveyor belt is formedfrom a trough into a pipe.

In some embodiments, the centering structure 202 and its attachment tothe bridging belt may be configured in such a way that the combinationhas sufficient flexibility to pass around pulleys or guide wheelswithout being subjected to excess strain.

FIG. 2c shows in elevation a partial longitudinal section of a length ofvertical pipe conveyor, with flexible centering arches 202 supportingthe bulk material 203 in a series of discrete cells. The centeringarches 202 may be configured to at least span the dimension between twoopposing walls of the pipe tube formed by the pipe belt 205. Spaces 206within the arches 202 may be partially filled with material 203 duringthe loading of the conveyor, or in the course of the pipe's progress.Material 203 held in the segment defined by adjacent arches maypartially fill the space so defined. In examples where the designer'sintent is to reduce the weight of carried material relative to theavailable longitudinal tensile strength of the pipe belt, a load feedermay be used to limit the level of fill of each segment.

In some examples, the bridging belt 201 may be constructed from a fabricconveyor belt or a steel cord conveyor belt of relatively low strengthcompared to that of the pipe conveyor belt. In those examples, thebridging belt may be configured to be supported against gravity withinthe pipe conveyor belt 205 by the friction developed between thebridging belt and the pipe conveyor belt under the internal outwardpressure exerted by the column of material 203 within the pipe belt. Insome examples, the bridging belt 201 may be configured to have at leastsufficient longitudinal strength to support its own weight as well asthat of the attached centering structures 202 over the greatest freelysuspended height that the bridging belt encounters within the conveyingsystem.

In other embodiments, the centering structures 202 may be configured tobe at least partially compressed by the enclosing pipe belt 205 so thatthere is sufficient frictional grip between the pipe belt and thecentering structures to support the combined weight of the bridging belt201 and the centering structures. In such embodiments the longitudinalstrength of the bridging belt 201 may be reduced.

FIG. 2d shows in elevation a longitudinal section of a length ofvertical pipe conveyor, with centering structures 202 configured toallow higher amounts of traction to be applied via intermediate frictiondrives, such as traction drives. In such an embodiment, a designer'sconcern may be to stiffen the pipe tube against lateral pressure appliedby an intermediate traction drive. Traction drives rely on tangentialfriction between the driving and the driven surfaces, so if higherinward force can be applied to the conveyor pipe without unduedeformation of the pipe shape, then a greater amount of traction can beapplied via friction at each intermediate drive. A difficulty forvertical pipe conveyors is that for the proportions found in most pipeconveyors, the silo effect prevents the bulk material from developingwall pressures of more than about one half of a pound per square inch.This low level of internal pressure provides insufficient lateralresistance to allow the intensity of tractive force yield that adesigner might desire. By spacing the centering structures 202 at aclose pitch and selecting an appropriate shape (e.g., an arch shape) andbending stiffness of the material forming the centering structure, thecentering structures 202 support the facing walls against lateralcompression, and a substantial increase may be obtained for thepermissible normal traction forces pressing inward on the pipe walls. Anappropriate bending stiffness for the centering structures 202 may allowsufficient flexibility that arch structures for the centering structures202 could still deflect away from the pipe wall if a lump of materialbecame pinched between the wall and the arch, rather than the pipe walldeveloping a protrusion.

Still with reference to FIG. 2d , in a preferred embodiment the pipebelt 205 takes the form of a rounded rectangular section, with thetraction drives biased against opposing flattened walls of the tube 211,212, and the centering structures 202 spanning between these two walls.In this embodiment, the centering structures 202 may be formed fromplanar material such as conveyor belting attached by fasteners 204 to abridging belt 201 so as to provide an endless series of sinusoid-shapedarches. Transported bulk material 203 may be carried primarily on theopen side of the centering structures 202, but also to some extentwithin any open spaces 206 such as those left on the “closed” side ofcentering structures 202. To better distribute the normal tractionforces, a pair of opposed traction belts 207 (providing wider loaddistribution than the traction tires shown in FIG. 9a ) driven byintermediate drive pulleys 208, tensioned by tail pulleys 209, andbiased against the flattened-from pipe belt by two or more pressingrollers 210 may be desirable, where the pressing length of the tractionbelts may preferably be a non-integer multiple of the centering pitch ofthe centering structures 202. Another advantage of such a centeringconfiguration is that it may help to stabilize the form of the belt tubeand transfer traction shear forces from the more shear-flexibleoverlapped walls 212 to the stiffer simple medial wall 211 of the belttube.

FIG. 3a shows a transverse section of a pipe conveyor belt 305 in amaterial loading zone. This figure illustrates how an open arch 302 mayprovide a route for lumpy material 303 to avoid being pinched by theenclosing walls of the pipe belt.

FIG. 3b shows a transverse section of pipe conveyor where the pipe belt305 forms a rounded rectangle about an enclosed centering structure 302.

FIG. 3c shows a perspective view of a pattern for a flat material 306that is formed into a centering structure, in this case a centeringarch, configured to fit in a pipe conveyor whose transverse section is arounded rectangle. To provide for smaller gaps between the sides of thecentering arch and the pipe wall, the pattern may include lobes 307configured to match the rounded sides of the pipe belt.

FIG. 4 shows a length of the open trough of a pipe conveyor belt 405,where the centering structures 402, such as centering arches, areattached directly to the carry-side medial portion of the pipe conveyorbelt itself. Such an embodiment may be desirable in examples where thematerial to be transported by the pipe conveyor is of a relatively fineand uniform consistency, and is also not too sticky. Appropriate usesmay also include examples where cleaning of the carry surface of thepipe belt can be omitted. Typical applications for such an embodimentmay include ship loaders and un-loaders or conveyors for charging silosand bins with semi-finished raw product. Other appropriate uses wouldinclude applications where there are no significant maintenance-relatedconcerns about fixations to the pipe conveyor belt itself.

FIG. 5a shows another embodiment of a centering structure for a pipeconveyor of a rounded rectangular transverse section, where thecentering structure 502 takes the form of a fully-closed domed cylindersupported by a base 503. The stiffness of the cylinder may derive fromthe bending stiffness of the walls, or the cylinder may be filled with acompressible elastic material. An advantage of such a centeringstructure is that there is no opening or void where material can collectand would later need to be shaken out over the conveyor system'sdischarge chute.

FIG. 5b shows a partial longitudinal section of a lateral elevation ofthe centering structure 502 illustrated in FIG. 5b . The centeringstructure 502 may be attached to a bridging belt 501 and enclosed in apipe belt. The base 503 of the centering structure 502 may take the formof one or more footings integrally molded with the cylinder.

FIG. 6a shows a transverse sectional view of a centering structure 602positioned in a pipe belt 605 that has a traditional circular transversesection.

FIG. 6b shows a perspective view of the centering structure 602 of FIG.6a . The centering structure 602 may be a flexible arch carried on abridging belt that is narrow relative to the circumference of the pipetube. In order for the centering structure 602 and the bridging belt 601to both rest stably on the bottom of the trough of the pipe belt beforethe loading area and to conform to the circular shape of the pipe belt,the mounting flanges 603 of the centering structure 602 and the bridgingbelt 601 may both be narrow relative to the circumference of the pipeform. First and second substantially circular portions of the centeringstructure 602 may be joined at a common apex by a narrow connectingportion 604.

FIG. 6c shows a lateral elevation of the centering structure 602 of FIG.6b mounted on the bridging belt 601. In this view, the centeringstructure 602 may have a triangular profile as shown, or else an archedprofile. In the case of an arched profile, the first and seconddisc-like portions of the centering structure 602 may be more ellipticalin form.

FIG. 7 shows a lateral elevation of a centering structure 702 configuredfor attachment by adhesion to a bridging belt 701. The arrows indicatethe slight downward load that the carried material may exert on thecentering structure 702. For this direction of loading, there are nosignificant prying forces that tend to open the adhered joints. Such aconfiguration may be desirable where a designer wishes to avoidmechanical fasteners that penetrate the bridging belt 701. In someexamples, the same form of centering structure 702 may be attached byadhesion directly to the carry-side medial portion of the pipe beltitself.

FIG. 8 illustrates an embodiment where the centering structures arecentrally rather than laterally attached to the longitudinal connectors.A series of spherical centering structures 802 is connected by a wirerope 801 passing through diametral axes of the spherical centeringstructures 802, like beads on a string. Spherical centering structures802 may be most suitable for a pipe conveyor that has a circularcross-section. The centering structures 802 may be configured to beflexible and compressible relative to the stiffness of the pipe beltwalls. Many variations of this embodiment are possible, including havingmore than one connection between each pair of centering structures andsubstituting ropes, chain or other elongate members in place of wirerope. In many examples, the centering structures are mounted on thelongitudinal connectors so that the centering structures are mountedsubstantially symmetrically with respect to the longitudinal connectors.Also, the centering structures 802 may be configured to have any formand attachment point to the elongate members that facilitates consistentpositioning of the centering structures 802 in manner that results inthe centering structures 802 spanning across the pipe section.

At points along the conveyor system where the assembled string 800 isnot guided by virtue of its enclosure within the formed pipe, the stringmay be guided by one or more guide wheels 803. Such guide wheels 803 maybe configured to have a first set of grooved peripheral surfaces 804 foraccepting the elongate portion of the assembled string, as well as asecond set of peripheral surfaces or recesses 805 configured to acceptthe passing centering structures. The circumferential pitch of theserecesses may match the linear pitch of the centering structures on thecable. In some embodiments, the guide wheel 803 may be driven only bythe passage of the assembled string.

FIG. 9a illustrates implementation of the centering structure andbridging belt principle in a vertical pipe conveyor system. In FIG. 9a ,features of a vertical pipe conveyor system 900 are omitted in order tohighlight the centering structure feature. However, omitted conventionalfeatures, such as a supporting structure, would be known to thoseskilled in the art. The vertical pipe conveyor system may have a tailend with a tail pulley 907 at a tail area of the conveyor, and a headpulley 906 at an elevation higher than the tail pulley. Material meteredfrom a feeding device 911 may be loaded at a loading zone 916, and maybe conveyed along the path of the pipe conveyor to be discharged at thehead area 904.

A pipe belt 905 may transition from a flat profile at the exit from thetail pulley 907, through a troughed profile in the loading zone 916 andinto a pipe profile at the end of the transition zone 917. At the pipeclosing point or zone, the pipe profile may be achieved by guiding firstand second lateral parts of the pipe belt to partially fold over eachother in the manner known for pipe belts. In some embodiments thecross-sectional shape of the pipe may be a rounded rectangular form.

A continuous, longitudinally spaced-apart series of centering structures902 may be attached to and carried by a bridging belt 901. The centeringstructures 902 and the bridging belt 901 may take a range of forms asdescribed elsewhere in this specification. The centering structures 902are configured to enable the natural bridging behavior of the carriedbulk material at steep or vertical portions of the pipe conveyor.

The bridging belt 901 may run external to the pipe conveyor belt and incontact with the carry side of the pipe conveyor belt when traversingthe tail pulley 907, so that the bridging belt lies flat on the bottomof the conveyor trough in the loading zone 916 and the centeringstructures 902 protrude upwards into the volume of the pipe trough. Inthe loading zone, the feeding device 911 may meter the material into thebelt trough and over the centering structures 902 so that the belttrough is filled to the desired degree. Downstream of the loading zone916, the lateral portions of the pipe belt may be folded over to form apipe or tube enclosing the series of centering structures 902. Thecentering structures 902 now divide the stream of carried material 903into discrete segments or cells to some significant degree.

The conveyor belt may be formed into a pipe and guided by conventionalpipe belt idler sets 910 through those parts of the pipe conveyor systemwhere the conveyor belt runs as a pipe. In steep and vertical parts ofthe pipe conveyor route, the centering structures 902 sustain bridgingof the bulk material so that the material may traverse from one level toanother in substantially stable segments or cells. Although somematerial may trickle through from a higher segment to a lower segment,this negligible backward flow does not significantly detract from thesubstantially stable nature of the material transport from one elevationto another.

An advantage of the segmented mode of material transfer is that apredetermined amount of space 918 may remain within a loaded pipe beltby virtue of the metered loading and also due to spaces within thecentering structures 902. This space may prevent dense packing of thematerial and facilitate more flexible traverses by the loaded pipe beltthrough vertical curves and between guidance means such as idler rings.

At a pipe-opening point or zone 919, the pipe belt may be opened in theconventional manner while the bridging belt 901 continues to progresstowards the head pulley 906 while resting on the pipe belt. At the headpulley 906 the material load discharges and the path of the bridgingbelt 901 may diverge from that of the conveyor belt 905. This separationof the two belts 901, 905 may be configured to provide space forcleaning of the conveyor belt 905, and to allow the conveyor belt 905 totraverse additional drive pulleys if necessary.

The bridging belt 901 may be guided around a bend pulley 908 and thenaround a guide wheel 909. The guide wheel 909 may position theattachment-free face of the bridging belt on the medial portion of theconveyor belt in the transition zone 914 where the conveyor belt isbeing re-formed into a pipe belt. The bridging belt may then be guidedaround the return portion of the conveyor system by being carried withinthe empty pipe belt. As the pipe belt approaches the transition zone 920at the end of the return route, the pipe belt is opened to a flattenedprofile so that the bridging belt and the conveyor belt may traverse thetail pulley 907 together.

Returning to FIG. 9a , one or more friction drives 912 or 913 may bepositioned proximate the conveyor pipe 900 along the vertical orinclined section of the pipe conveyor system. Each friction drive 912and 913 may include a friction drive tire. In some other examples, thefriction drives may comprise a pair friction drive belts biased againstopposing faces of the pipe conveyor belt. This engagement of thefriction drives with the conveyor pipe results in the friction drivesapplying pushing forces to the conveyor pipe 900. These forces help pushthe belt 905, and any material 903 contained therein, from the firsthorizontal section to the second horizontal section.

In some other embodiments of the pipe conveyor system of FIG. 9a , thebridging belt 901 may be replaced by the types of wire rope-mountedcentering configuration described in connection with FIG. 8.

In some other embodiments of the pipe conveyor system of FIG. 9a , theflow of material may be from a higher elevation to a lower elevation,with the tail pulley 907 and feeding device 911 at the higher elevation.

FIG. 9b shows in cross section the pipe tube of FIG. 9a that encloses acentering structure and bridging belt. The rounded rectangular form ofthe pipe belt 905 may be maintained through guidance by idler sets, forexample by six-idler sets, only three of which 910 are visible at thistransverse section. Also visible in this section are the bridging belt901 and the face of a centering arch 902, showing the rounded lobe 921configured to match the inside curvature of the pipe belt.

FIG. 10 shows a more detailed view of the head end of the pipe conveyorof FIG. 9a to better illustrate that arrangement for separating thepaths of the bridging belt and the pipe belt at the discharge pulley ofthe pipe conveyor system. A tensioning pulley 922 is added to theconfiguration shown in FIG. 9a . At the head pulley 906, the materialload discharges and the path of the bridging belt 901 may diverge fromthat of the conveyor belt 905. This separation of the two belts may beconfigured to provide space for cleaning of the conveyor belt, forshake-out of the bridging belt, to allow the conveyor belt to traverseadditional drive pulleys if necessary, and/or to provide for tensioningof the bridging belt.

After traversing the head pulley 906, the conveyor belt may commence areturn path by passing next to a belt-cleaner support pulley 926 againstwhich one or more belt cleaners 925 are biased. A dribble-collectionapparatus 927 may be configured to capture material dislodged by thebelt cleaners, and return the material to the main flow, either by agravity chute or by a powered means, such as an auxiliary belt or auger.The conveyor belt 905 may then continue to a transition zone wheretransition idlers may form it into a pipe form for the return route tothe tail of the conveyor system.

Part-way around the head pulley 906, the path of the bridging belt maydiverge from that of the conveyor belt by passing over of a bend pulley908. As the bridging belt 901 spans the distance between the head pulley906 and the bend pulley 908, it may overhang a portion of a dischargechute 924. One or more agitating wheels 923 may be biased against theinner side of the bridging belt to shake carry-back material free fromof the bridging belt and from any open spaces within the centeringstructures 902. The path of the bridging belt 901 may then take thebridging belt 901 around a tensioning pulley 922, which may be providedto maintain a desired tension in the bridging belt 901. A guide wheel909 may then position the attachment-free face of the bridging belt 901on the medial portion of the conveyor belt 905 in the transition zone914 where the conveyor belt 905 is being re-formed into a pipe belt.

The guide wheel 909 may be configured to have a first set of peripheralsurfaces 930 arranged to contact and redirect the outer face of thebridging belt 901, as well as a second set of peripheral surfaces orrecesses 928 configured to accept the passing centering structures 902.The circumferential pitch of these recesses 928 may match the linearpitch of the centering structures 902 on the bridging belt 901. In someembodiments, the guide wheel 909 may be driven only by the passage ofthe bridging belt 901. Since both the centering structures 902 and thebridging belt 901 are likely to be quite flexible, and since thebridging belt 901 carries only a low tension, no damage is likely toaccrue to any components should the pitch synchronization between thecentering structures 902 and the guide wheel recesses 928 somehow belost.

The bridging belt 901 may then be guided around the return portion ofthe conveyor system by being carried within the empty pipe belt.

FIG. 11 shows, in an isometric schematic, another example of anarrangement for separating the paths of the bridging belt and theconveyor belt at the discharge pulley of the pipe conveyor system. Inthis arrangement, the bridging belt 1101 continues in a straight pathbeyond the head pulley and over the discharge chute, leaving room on thehead pulley for conventional belt-cleaning arrangements (which are notshown in the figure). In this figure, most of the centering structures1102 on the bridging belt 1101 have been omitted from the illustration,with only a few having been illustrated in order to better show thetwisting path of the bridging belt 1101.

For the arrangement of FIG. 11, a horizontally-oriented bend pulley 1103may guide the bridging belt 1101 through a ninety-degree twist as thebelt passes above the discharge chute 1104. This allows material thatmay have been resting on the upper surface of the bridging belt 1101 tofall off into the chute. The bend pulley 1103 may preferably be equippedwith guide flanges on each face to help align the bridging belt 1001with the bend pulley 1103 and to support part of the freely-suspendedweight of the bridging belt 1101. The bend pulley 1103 may be equippedwith a take-up mechanism in order to provide tensioning to the bridgingbelt 1101.

After the bridging belt 1101 passes around the bend pulley 1103,additional bend pulleys 1108, 1110 may guide the bridging belt to skirtthe discharge chute 1104 and be led to a guide wheel 1107. To providethe desired bridging belt routing, these bend pulleys 1108, 1110 maytake advantage of the high flexibility of the bridging belt 1101 and bealigned on axes that are skewed from orthogonal axes associated with thehead pulley 1106. The guide wheel 1107 may be configured similarly tothe guide wheel 909 described in FIG. 9a , and may include guide flangesto help track the bridging belt 1101. The guide wheel 1107 may bemounted on a skewed axis in order to better conduct the bridging belt1101 on the desired path. Suitably-configured dribble troughs (not shownin the figure) may be installed if necessary under the path of thebridging belt between the bend pulley 1103 and the guide wheel 1107.

FIG. 12 is a schematic lateral elevation of the tail end of a pipeconveyor system upstream from the loading zone 1207, where alocally-convex conveyor path 1209 aids in holding the bridging beltstably on the bottom of the pipe conveyor trough. In FIG. 12, a bridgingbelt 1201 carries a series of centering structures 1202 by moving alongin contact with the carry face of the conveyor belt 1205. After emergingfrom the return pipe in the pipe-opening zone 1208, the bridging belt1201 may traverse the tail pulley 1206 by riding on the outside of theflattened conveyor belt. In traversing the tail pulley, the bridgingbelt 1201 may be biased against the conveyor belt by the tensioningapplied elsewhere in the conveyor system to the bridging belt 1201.Downstream from the tail pulley 1206, a bend pulley 1203 may deflect thebridging belt and the conveyor belt along a locally-convex path 1209before the mated belts enter the loading zone 1207 where feeding andmetering equipment 1204 may fill the conveyor trough to the desiredlevel, at least partially burying the centering structures. The presenceof the convex curve over the bend pulley 1203, combined with theproximity of the tail pulley 1206 and the tension in the bridging belt1201, will tend to hold the bridging belt 1201 properly seated on theconveyor belt 1205 while material is loaded at the loading zone 1207.While it may be most elegant for the bridging belt to remain well-seatedon the bottom of the conveyor belt trough during loading, there will notbe any significant consequences if some bulk material does intrudebetween the conveyor belt and the bridging belt during loading or evenlater on along the conveying path.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles. For example, althoughthe figures have depicted vertical conveyors, the same principlesdescribed herein may be applied to inclined sections of pipe conveyorswhere the inclines are greater than the surcharge angle of the materialbeing transported. Further, while FIG. 9a shows the pipe conveyor ashaving one inclined section and two horizontal sections, the systemdescribed above could be used with pipe conveyor systems that havemultiple inclined and horizontal sections.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of theembodiments of the present invention, and do not create limitations,particularly as to the position, orientation, or use of the inventionunless specifically set forth in the claims. Connection references(e.g., attached, coupled, connected, joined, and the like) are to beconstrued broadly and may include intermediate members between aconnection of elements and relative movement between elements. As such,connection references do not necessarily infer that two elements aredirectly connected and in fixed relation to each other. Reference to “a”or “one” is not intended to limit the description to one only, but maybe interpreted as including “one or more than one” unless otherwisespecifically indicated by description or context of the relatedstructure or function.

In some instances, components are described with reference to “ends”having a particular characteristic and/or being connected with anotherpart. However, those skilled in the art will recognize that the presentinvention is not limited to components which terminate immediatelybeyond their points of connection with other parts. Thus, the term “end”should be interpreted broadly, in a manner that includes areas adjacent,rearward, forward of, or otherwise near the terminus of a particularelement, link, component, part, member or the like. In methodologiesdirectly or indirectly set forth herein, various steps and operationsare described in one possible order of operation, but those skilled inthe art will recognize that steps and operations may be rearranged,replaced, or eliminated without necessarily departing from the spiritand scope of the present invention. It is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative only and not limiting. Changes indetail or structure may be made without departing from the spirit of theinvention as defined in the appended claims.

What is claimed is:
 1. A conveyor system, comprising: a pipe conveyorincluding a head end, a tail end positioned at an elevation differentfrom the head end, and an inclined section between the head end and thetail end; the pipe conveyor including a conveyor belt comprising a firstportion and a second portion, and the conveyor belt forming a pipe shapewhen the first and second portions of the conveyor belt are overlapped;the pipe shape extending from a pipe closing point to a pipe openingpoint and enclosing a plurality of longitudinally spaced-apart centeringstructures; at least one of the plurality of longitudinally spaced-apartcentering structures enabling self-bridging of a bulk material carriedin a pipe volume above the at least one of the plurality longitudinallyspaced-apart centering structures; and the self-bridging of said bulkmaterial causes a weight of said bulk material to be primarily supportedby interaction of said bulk material with walls of the pipe shape. 2.The conveyor system of claim 1, wherein the at least one of theplurality of longitudinally spaced-apart centering structures issufficiently flexible to conform to the pipe shape when a lump of bulkmaterial is pinched between the at least one of the pluralitylongitudinally spaced-apart centering structures and the conveyor belt.3. The conveyor system of claim 1, wherein the plurality oflongitudinally spaced-apart centering structures is carried on at leastone endless elongate connector not joined to the conveyor belt.
 4. Theconveyor system of claim 3, wherein the at least one endless elongateconnector comprises at least one bridging belt that carries theplurality of longitudinally spaced-apart centering structures on oneface of the at least one bridging belt and an opposing face of the atleast one bridging belt rests against a carry-side medial surface of theconveyor belt.
 5. The conveyor system of claim 4, wherein the at leastone of the plurality of longitudinally spaced-apart centering structurescomprises mounting flanges, wherein the mounting flanges and the atleast one bridging belt are narrower than a circumference of the pipeshape.
 6. The conveyer system of claim 5, wherein the at least one ofthe plurality of longitudinally spaced-apart centering structuresfurther comprises first and second substantially circular portionsjoined at a common apex by a narrow connecting portion.
 7. The conveyorsystem of claim 3, wherein the at least one endless elongate connectorcomprises a wire rope, and the plurality of longitudinally spaced-apartcentering structures comprises a plurality of spherical centeringstructures in which the wire rope passes through diametrical axes of theplurality of spherical centering structures.
 8. The conveyor system ofclaim 7, further comprising at least one guide wheel having peripheralrecesses that are sized to accept at least one of the plurality ofspherical centering structures as the at least one of the plurality ofspherical centering structures passes the at least one guide wheel. 9.The conveyor system of claim 3, further comprising at least one bendpulley situated beyond a discharge pulley of the conveyor system thatguides the at least one endless elongate connector on a path displacedaway from a path of the conveyor belt.
 10. The conveyor system of claim3, wherein the at least one of the plurality of longitudinallyspaced-apart centering structures attaches to the at least one endlesselongate connector in such a way as to dispose the at least one of theplurality of longitudinally spaced-apart centering structuressubstantially symmetrically about the at least one endless elongateconnector.
 11. The conveyor system of claim 1, wherein each of theplurality of longitudinally spaced-apart centering structures isdirectly attached to a carry-side medial surface of the conveyor belt.12. The conveyor system of claim 11, wherein at least one of theplurality of longitudinally spaced-apart centering structures is adheredto the carry-side medial surface of the conveyor belt.
 13. The conveyorsystem of claim 1, further including at least one intermediate frictiondrive at an inclined section of the pipe conveyor, and the least oneintermediate friction drive engages external surfaces of the conveyorbelt.
 14. The conveyor system of claim 13, wherein the plurality oflongitudinally spaced-apart centering structures is closely spaced andconfigured to stiffen opposing walls of the pipe belt against a biasingapplied by traction components of the at least one intermediate frictiondrive.
 15. The conveyor system of claim 14, wherein the at least one ofthe plurality of longitudinally spaced-apart centering structurescomprises an arch shaped centering structure.
 16. The conveyor system ofclaim 15, wherein the at least one intermediate friction drive comprisestraction drives biased against opposing flattened walls of the conveyerbelt, and the plurality of longitudinally spaced-apart centeringstructures span between the flattened walls.
 17. The conveyor system ofclaim 13, wherein the at least one intermediate friction drive comprisesa friction drive tire.
 18. The conveyor system of claim 1, wherein atleast one of the plurality of longitudinally spaced-apart centeringstructures comprises one or more footings integrally molded with acylinder.
 19. The conveyor system of claim 1, further comprising afeeding device that feeds the bulk material at a rate that onlyfractionally fills a plurality of carrying segments defined by theplurality of longitudinally spaced-apart centering structures.
 20. Theconveyor system of claim 1, wherein the elevation between the head endand the tail end forms an angle that is greater than a surcharge angleof the bulk material carried on the conveyor.